This invention relates to a hydraulic damper and particularly to improvements in methods of manufactuure of a valve mechanism in the hydraulic damper.
One prior art hydraulic damper comprises a cylinder, a piston slidably disposed in the cylinder and partitioning the interior of the cylinder into first and second oil chambers, a piston rod secured to the piston and extending through the first oil chamber to the outside, a first damping force generating valve mechanism provided in the second oil chamber to control the oil flow between the second oil chamber and a reservoir chamber, and a second damping force generating mechanism mounted on the piston for generating a damping force in the extension stroke of the damper. The first damping force generating mechanism generates a damping force in the contraction stroke of the damper.
The first damping force generating mechanism typically comprises an annular disc or a valve member, an annular valve seat formed on a bottom member connected to one end of the cylinder, a spring biasing the valve member toward the valve seat, and a retainer supporting the spring and being mounted on the bottom member. For reliably mounting the retainer on the bottom member, the retainer usually has a generally hat shaped configuration having on one end a radially outwardly extending flange clamped axially between the cylinder and the bottom member, and on the upper end an aperture for permitting the liquid to flow therethrough. Further, there has been provided between the outer circumference of the valve member and the inner circumference of the retainer a valve guide having a plurality of angularly spaced and axially extending guide portions for slidably engaging with and supporting the outer circumference of the valve member. The valve guide is also retained by the retainer. However, it has been difficult to form a sufficient passage area for the oil flow, particularly between the upper end portions of the retainer and the valve guide. Further, since the valve guide and the retainer are separate parts, the manufacturing and assembling process are complicated